LOAN PORTFOLIO- Carrying Value of Purchased Credit Impaired Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	$ 8,858,123	$ 8,850,476	$ 8,886,873
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	146,640	158,174	165,818
Allowance for loan losses purchased credit impaired	(11,354)	(11,251)	(6,857)
Purchased Credit Impaired Loans, Net	135,286	146,923
Residential Portfolio Segment [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	3,163,208	3,290,957	3,296,031
Residential Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	143,176	153,991	162,676
Allowance for loan losses purchased credit impaired	(10,954)	(10,873)	(6,632)
Commercial Portfolio Segment [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	3,750,202	3,809,622
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	1,522,662	1,614,972	1,568,808
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable Impaired [Line Items]
Loans and Leases Receivable, Gross	3,464	4,183	3,142
Allowance for loan losses purchased credit impaired	$ (400)	$ (378)	$ (225)

Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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- Definition

The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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